Modular construction of process plants and other industrial process facilities is known. Generally, modular construction involves building numerous separate modules at a fabrication site, transporting the modules from the fabrication site to the plant site, and then coupling the modules together at the plant site to erect the process plant. Modular construction is use to construct process plants worldwide in many onshore and offshore applications, including, but not limited to petroleum processing and refining, chemical processing, mineral processing, and forest product processing.
Conventionally, modules are fabricated by fastening structural members, such as steel beams, together to create a three-dimensional, skeleton-like frame. The frame is generally a multi-story rectangular grid of connected vertical and horizontal beams forming the module. The frame is usually constructed outdoors in a prepared industrial yard, commonly called a “module yard” or “mod yard” for short. Large mod yards can range up to a hundred hectares with dozens of portable cranes, and workforces as large as 1,000 members.
After the frame is fabricated, it is moved to a location in the mod yard and supported on blocks, typically 1 m high. Temporary ladders, scaffolding, and/or platforms are erected so workers can climb to locations within the frame to install permanent walkways (if included) and piping and/or other equipment mounts and supports. Afterwards, piping and other equipment are installed, followed by insulating the liquid carrying components and various electrical and instrumentation systems.
Cranes are required to lift the various lengths of pipe and other equipment up and into the frame and place them as close as possible to the position of where they will be installed. Positioning the equipment in the frame at the installation location is limited by the vertical and horizontal beams that make up the frame. Additionally, temporary or permanent lighting may be setup around the yard to allow performing work at night. And tarpaulins and portable heaters may be used to limit worker exposure to inclement weather.
The size and configuration of each module depends on the functional requirements of the related portion of the process plant where the module will be installed. Often the modules are designed to be as large as the highway transportation network will allow. For example, modules can be 7.3 m wide, 7.3 m high, and 40 m long, and weighing up to 150.00 kg. The typical time to construct a module can vary considerably depending on the scope of work required, as well as workforce availability. A typical target is four to eight weeks depending on the module.
While modularized plant construction is desirable because of significantly reduced construction costs and reduced time to complete construction that are realized with modularized plant construction, there are many drawbacks to current modularized construction methods. Most of the drawbacks relate to initially constructing the individual modules in multistory frames and then relocating the modules for installing equipment. This method of construction reduces worker efficiency and raises the risk of job-site accidents due to many factors.
These factors include significant costs and safety risks in moving multi-story steel structures within large and congested mod yards. These factors also include the time needed to setup temporary ladders, stairs, and scaffolding that is required for workers to perform work on the frame. Additionally, frequently climbing ladders, stairs, and scaffolding contributes to worker fatigue and accidents, especially when work is performed during inclement weather or at night.
Further, all work is performed outside all across the mod yards, and completion of the work is subject to bad weather conditions including temperature and precipitation. Additionally, often workers are required to walk considerable distances from their marshalling point to a location at the mod yard to perform work. This walking may be through mud, snow, or ice.
Further yet, multiple cranes and highly skilled operators are required for many of the crews to place and move heavy equipment while weaving the equipment through the openings of the module's skeleton frame in order to place the equipment. And work that is performed simultaneously on multiple levels of frame at times must be stopped to prevent injury from tools or equipment falling on workers below. Also, any tools or equipment that fall could fall in mud or snow, risking loss or damage.